package com.aruba.jniapplication;
public class JniDemo {
static {
// System.out.println(System.getProperty("java.library.path"));
System.load("C:\\Users\\tyqhc\\Documents\\workspace\\JniApplication\\app\\src\\main\\java\\com\\aruba\\jniapplication\\myjni.dll");
// System.loadLibrary("myJni");
}
public static native String getStringFromC();
public native String getStringFromC2();
public static void main(String[] args) {
System.out.print(getStringFromC());
}
}
image.png
#include "my_jni.h"
#include <string>
using namespace std;
JNIEXPORT jstring JNICALL Java_com_aruba_jniapplication_JniDemo_getStringFromC
(JNIEnv* env, jclass jclz) {
//新建一个string对象
string s = "hello from C++";
jstring jstr = env->NewStringUTF(s.c_str());
return jstr;
}
//非静态native方法
JNIEXPORT jstring JNICALL Java_com_aruba_jniapplication_JniDemo_getStringFromC2
(JNIEnv* env, jobject jobj) {
//获取jclass
jclass jclz = env->GetObjectClass(jobj);
string s = "hello from c++ by jobject";
jstring jstr = env->NewStringUTF(s.c_str());
return jstr;
}
package com.aruba.jniapplication;
public class JniDemo {
static {
// System.out.println(System.getProperty("java.library.path"));
System.load("C:\\Users\\tyqhc\\Documents\\workspace\\JniApplication\\app\\src\\main\\java\\com\\aruba\\jniapplication\\myjni.dll");
// System.loadLibrary("myJni");
}
public static native String getStringFromC();
public native String getStringFromC2();
public static void main(String[] args) {
System.out.print(getStringFromC());
JniDemo jniDemo = new JniDemo();
System.out.print("\n");
System.out.print(jniDemo.getStringFromC2());
}
}
public String javaStr = "javaStr";
public native String changeJavaString();
JNIEXPORT jstring JNICALL Java_com_aruba_jniapplication_JniDemo_changeJavaString
(JNIEnv*, jobject);
JNIEXPORT jstring JNICALL Java_com_aruba_jniapplication_JniDemo_changeJavaString
(JNIEnv* env, jobject jobj) {
//获取jclass
jclass jclz = env->GetObjectClass(jobj);
//获取fieldId 第二个参数为java中的变量名;第三个参数为签名
jfieldID jfieldID = env->GetFieldID(jclz,"javaStr","Ljava/lang/String;");
// 得到javaStr 对应的值
// GetXXXField
jstring jStrObj = (jstring)(env->GetObjectField(jobj, jfieldID));
//将jstring转换为c++的string
string str = env->GetStringUTFChars(jStrObj, NULL);
//在后面拼接一个字符串
str += " hello by c++";
//将c++的string转为jstring
jstring newStr = env->NewStringUTF(str.c_str());
//将java的变量值改变
env->SetObjectField(jobj, jfieldID, newStr);
//释放
env->ReleaseStringUTFChars(newStr, str.c_str());
//返回出去
return newStr;
}
Java属性与方法签名列表.png
package com.aruba.jniapplication;
public class JniDemo {
static {
// System.out.println(System.getProperty("java.library.path"));
System.load("C:\\Users\\tyqhc\\Documents\\workspace\\JniApplication\\app\\src\\main\\java\\com\\aruba\\jniapplication\\myjni.dll");
// System.loadLibrary("myJni");
}
public static native String getStringFromC();
public native String getStringFromC2();
public String javaStr = "javaStr";
public native String changeJavaString();
public static void main(String[] args) {
System.out.print(getStringFromC());
JniDemo jniDemo = new JniDemo();
System.out.print("\n");
System.out.print(jniDemo.getStringFromC2());
System.out.print("\n");
jniDemo.changeJavaString();
System.out.print(jniDemo.getJavaStr());
}
public String getJavaStr() {
return javaStr;
}
}